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1、11.BeltdrivesVocabulary:versatility[9v:sE`tilEti]多功能性flexibility[7fleksE5biliti]适应性，弹性tolerance[5tClErEns]公差critical[5kritikEl]严格的shock[FCk]冲击relatively[5relEtivli]相对的means[mi:nz]手段，方法leather[5leTE]皮革fabric[5fAbrik]纺织物conventional[kEn5venFEnl]常规的vertica
2、l[5vE:tikEl]垂直的constant[5kCnstEnt]不变的slippage[5slipidV]滑动inherent[in5hiErEnt]固有的precise[pri5sais]精确的pulley[5puli]滑轮plane[plein]平面wrap[rAp]缠绕Text:Beltdrivesofferamaximumofversatilityaspowertransmissionelements.Theyallowthedesignerconsiderableflexibilityin
3、locationofdriveranddrivenmachinery,andtolerancesarenotcriticalasisthecasewithgeardrives.Anotheradvantageofbeltdrivesisthattheyreducevibrationandshocktransmission.Furthermore,beltdrivesarerelativelyquiet.Largeflatleatherbeltswereingeneralusemanyyearsago,w
4、hentheusualpracticewastouseonelargeenginetodriveseveraldifferentpiecesofmachinery.Someleatherbeltsareinuseatthistimeaswellasflatsteel,rubber,plastic,andfabricbelts.Light,thinflatbeltsarepracticalonhighspeedmachinerywherevibrationmaybeaproblem.Vbeltsarepr
5、obablythemostcommonmeansoftransmittingpowerbetweenelectricmotoranddrivenmachinery.ConventionalVbeltsaremadeofrubber.Mostoften,bothdriveranddrivenpulleyslieinthesameverticalplane,andthespeedratioisconstant.SmoothflatbeltsandVbeltsdependonfrictiononthepull
6、eysandsomeslippageisinherentintheiroperation.Therefore,speedratiosarenotprecise.Mostheavydutypulleysaremadeofcastironorformedsteel.Notethatthecapacityofthebeltdriveisdeterminedbytheangleofwrap,α,onthesmallerpulley,andthatthisisparticularlycriticalfordriv
7、esinvolvingpulleysofgreatlydifferingsize,spacedcloselytogether.Appending:ConveyerBeltConveyer,mechanicalsystemfortransportingmaterialsfromonesitetoanother.Conveyersarewidelyusedinindustrialandbusinessoperations.Theyincludesimplechutes,theunpoweredrollerc
8、onveyersusedtomovecargoacrosssidewalksfromtruckstostores,andawiderangeofpoweredsystemsinwhichmaterialsarecarriedalongbybelt,bucket,screw,trolley,orotherarrangement.Pneumaticconveyersaretubesinwhichgoods—usuallyinafinelydiv
